LAKE PLANTS UPDATE: Slender Water Nymph
by Mike Prince, Watershed Chair
Sources: Ben Peterson, Aquatic Noxious Weed Specialist, King County Noxious Weed Control Program, Jen Parsons, Aquatic Plant Specialist, Washington State Department of Ecology
Most Prominent Lake Margaret Aquatic Plant = Najas guadalupensis (slender water nymph)
- Perennial native aquatic plant – lives year-round and for many years in shallow areas of Lake Margaret
- Spread across Lake Margaret over time by floating cuttings and seed. Hard to slow down since it doesn’t die off in the winter!
- Can grow from fragments, so harvesting should try to minimize fragment creation
- Fruit/seeds present in late summer
- Positives: native plant that adds good fish habitat and helps filter water
- Negatives: crowds out other plant diversity around the lake – more diversity is healthier; Impacts recreation by making boat launch and swimming from shores and docks less inviting.
- Removal and mitigation is possible and legal for 10′ wide areas of each homeowner’s shoreline with a simple “pamphlet permit” between July 16 – September 30. Ben recommends the early part of the window before seeding and working hard to remove fragments from the lake since it regrows from fragments.
- More details on recommended removal methods from Ben are listed on the LMCPC Web page for Lake Plants. (Link to Web site page)
- Ben Petterson’s Slides from the February Lake Margaret Board Meeting presentation can be viewed here: (Link to PDF)
— From: Ben Peterson, Monday March 2, 2020 —
Thanks again for the opportunity to come out to Lake Margaret and share with you all what I know about aquatic plants at the lake. This email will serve to address many topics that I said I would follow-up on. Feel free to share all this information with the community. In no particular order:
- View the PDF version of the slide show presentation >
- Plant list on the WA Ecology lake data page: https://fortress.wa.gov/ecy/coastalatlas/tools/LakeDetail.aspx
- King County web page on the Lake: https://green2.kingcounty.gov/SmallLakes/lakepage.aspx?SiteID=26
- Info on Najas guadalupensis (slender water nymph)the native plant that has been growing very robustly at Lake Margaret the past few years:
- From An Aquatic Plant Identification Manual for Washington’s freshwater plants:
- Fruit/seeds: oval shaped about 3 mm long. Present in late summer.
- From Jen Parsons (the WA State Dept of Ecology Aquatic Plant Ecologist):
- N. guadalupensis is actually a perennial. So, my guess it that is likely what is in Lake Margaret, since it also didn’t seem to be making seed.
- I don’t have any reason to believe it is non-native – it looked like one of the natives at the time (during her 2015 and 2012 surveys)
- I have seen previous year’s growth still hanging at the lake bottom in early April (in Black Lake, Thurston Co), and this has also been noted in the Midwest
- Info on water nymph control:
- https://lakebottomblanket.com/lake-weeds-identification/submerged/southern-naiad-najas-guadalupensis/ (Web site from some company in New Jersey that sells bottom blankets. The web site says that if you cut (and harvest?) Najas at just the right time of the year “before the seeds are mature the removal method can have a huge impact.“ )
- Texas A&M page on water nymph control: https://aquaplant.tamu.edu/management-options/how-to-control-brittle-waternymph/
- Weed Roller:
- WDFW (in their permit booklet) allows up to 2500 sq ft to be cleared (which works out to be 24’ radius of a 270 degrees arc)
- Attaches to the corner of a dock.
- http://www.weedroller.com/ (Weed Roller costs ~ $4,500)
- https://weedersdigest.com/lake-groomer-lake-weed-roller/ (Lake Groomer cost~ $4,000)
- You can order the aquatic plant ID book from WA Ecology (called “An Aquatic Plant Identification Manual for Washington’s Freshwater Plants”) from this web site: you can order it from this web site: https://prtonline.myprintdesk.net/DSF/ProductDetails.aspx?q0dmFiIMRMmOjUAFwvQB/9AE5l7YOYYYgzLEkERdf/m1RbRgmj4CwjTQJpJDwhVdCOqBuXKBSxBi8UPbgN1j+A==
- King Conservation District (which you all pay into) has a program called Urban Shorelines and Riparian Habitat Improvement Services. Check out their web page: https://kingcd.org/programs/better-water/urban-shorelines-riparian-habitat-improvement-services/ In addition to describing their program the bottom of the web page also has links to other resources such as the King County Go Natives web page (and there is also the KC Natural Yard Care page).
- King County also has a web site that may help with native plant landscaping, if that is something you are hoping to do on your waterfront: https://green2.kingcounty.gov/gonative/index.aspx
- A link to the WDFW “Aquatic Plants and Fish Booklet” permit. https://wdfw.wa.gov/licenses/environmental/hpa/types/aquatic-plantsThis is the free permit that describes how aquatic weeds (weeds growing out of standing water or deeper such as iris that might be growing out of standing water or water lily plants or milfoil) can be controlled physically (it doesn’t cover herbicide use). To be in compliance with this permit/booklet you need to print it up, read it and follow the rules in it. If you want to do physical weed control work that is outside the scope (in terms of physical area or calendar timing) of the permit/booklet the you would have to get a Standard HPA permit: https://wdfw.wa.gov/licenses/environmental/hpa/types . The “Aquatic Plants and Fish Booklet” permit covers physical weed control methods including:
- Hand pulling of weeds that pull up the roots when growing in standing water
- Weed mats/bottom screens
- Weed Rollers (that thing that Chris mentioned)
- Clearing native plants using something like a big weed rake or a weed razor.
- There are different rules about how much area of plants can be removed or covered up depending if the plant is a listed aquatic weed (such as yellow flag iris, fragrant water lily, or Eurasian watermilfoil) and “Aquatic Beneficial Plants” which are native plants and non-native plants that aren’t noxious weeds.
- The “Aquatic Plants and Fish Booklet” does not really describe the different physical weed control methods that is regulates. For a pretty good description (with very outdated cost estimates) I will direct you to an archived version of the WA Dept. of Ecology web site: https://web.archive.org/web/20171108092108/http:/www.ecy.wa.gov/programs/wq/plants/plantmgmt.htmlThis web page has a ton information on various weed control techniques, including herbicide. Unfortunately when WA Ecology re-did their web site about two years ago they removed all this great info. It’s a little outdated but at least it will give you an idea of what the weed control methods entail.
- Yellow flag iris control (a shoreline noxious weed that occurs at the lake):
- Here is the BMP: https://your.kingcounty.gov/dnrp/library/water-and-land/weeds/BMPs/yellow-flag-iris-control.pdf
- Here is the weed program web page: https://www.kingcounty.gov/services/environment/animals-and-plants/noxious-weeds/weed-identification/yellow-iris.aspx
- Info about the WDFW boat launch at Lake Margaret:
- Contact info for the North Puget Sound regional WDFW office (who may be able to help with potentially putting up a new sign at the boat launch notifying folks to make sure their boat and trailer is clean of weeds before accessing the lake) https://wdfw.wa.gov/places-to-go/weekender/north-puget-sound
- I can work with those who are interested in getting a new Aquatic Invasive Species sign for the boat launch (I recently got one put up at the Shadow Lake WDFW boat launch)
- I have attached a .pdf of the pertinent pages of an aquatic plant survey that was done in 1995.
- I have attached a list of contractors that claim to do weed control work in King County. We don’t endorse anyone on the list but it might be a place to start a search for a contractor. See the columns for info about who claims to do what.